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Hydrogen gas production generated from carbon-free molecules while utilizing solar energy provided a pathway for zero carbon emission energy. In photocatalytic hydrogen gas production, alcohol and oxygenated compounds as sacrificial agents are often added to accelerate the water splitting process while simultaneously decomposing to form H2 and CO2. However, the generation of CO2 requires an additional measure to curb carbon from being released into the atmosphere. This study evaluated the performance of TiO2 photocatalysts to generate hydrogen from NH3 solution as carbon-free molecules. The investigation is extended to alkylamines compounds as sacrificial agents. H2 is linearly produced from NH3 when using Pd/TiO2; however, the rate is reduced after a prolonged photocatalytic reaction. Alkylamines molecules are more susceptible for H2 production than NH3, with the reactivity increased from NH3 < triethylamine < diethylamine < ethylamine. Comparative analysis was also conducted on the amount of H2 and CO2 gases released from alkylamines and alcohols to indicate nitrogen-containing compounds viability as sacrificial agents for carbon-emission free sacrificial agents in photocatalytic water splitting reaction. [ABSTRACT FROM AUTHOR]

Today, vehicles especially diesel engines emitted a large amount of NOx in the urban areas. So, it is required to find ways such as SCR catalysts to reduce this hazard pollutant emission. In this work, a 3D model of cordierite/Pt SCR catalyst has been developed by using AVL FIRE software to analyze the NOx conversion efficiency. The simulation was performed based on experimental tests conducted on a single-cylinder engine. The exhaust gas from the engine that appears at the inlet of the catalyst was measured for E20B50D30 (20% ethanol, 50% biodiesel, 30% diesel) D100, E10D90, E20D80, B25D75 and B50D50 fuel blends at the engine speeds of 1800, 2150 and 2500 rpm under full load. The results showed that an increase in the engine's rotational speed resulted in a reduction of NOx conversion, and the conversion rate reaches its minimum value at speed of 2500 RPM for all fuel mixtures. Moreover, increasing the ammonia mass flow rate resulted in higher NOx conversion for all fuel mixtures. However, the effect of increasing ammonia flow rate from 0.2 to 0.3 kg/h on the NOx conversion is lower than that when the ammonia mass flow changes from 0.1 to 0.2 kg/h. The maximum NOx conversion rate was observed for the mixture containing 20% ethanol and 80% diesel at the rotational speed of 1800 RPM while the lowest conversion rate is observed for pure diesel fuel. According to the results, it was seen that the SCR catalytic process for fuel blends contained ethanol have a better performance to reduce the NOx pollutant compared to the mixtures containing biodiesel at lower engine speeds; but at higher rotational speeds ethanol and biodiesel has not a positive effect on the NOx conversion. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) of NO with NH3 on an activated coke supported V2O5 (V2O5/AC) catalyst was studied at 200 °C by in-situ diffuse reflectance infrared Fourier transform spectroscopy. Results indicate that NH3 is adsorbed in the forms of coordinated NH3, NH4 + and –NH2. V2O5 promotes formation of –NH2. NO is oxidized to NO2 in the presence of O2. –NH2 and NO2 are the intermediates of the SCR reaction. [ABSTRACT FROM AUTHOR]

V2O5/TiO2 catalysts with various vanadia loadings were prepared using inorganic precursor of vanadium by sol–gel method, and characterized by XRF, XRD, BET, Raman spectra and XPS techniques. Results demonstrated that the catalyst with 6.17 wt% vanadia had a high activity in the temperature range from 180 to 450 °C at a gas hourly space velocity of 10,000 h−1 and the activity was affected by increasing the space velocity at the temperature below 270 °C. All the catalysts showed high activity in the different temperature range under tested conditions. [ABSTRACT FROM AUTHOR]

Gold deposition on Hombikat UV100 was found to negatively affect the activity of this Anatase catalyst in selective photo-oxidation of cyclohexane. By ammonia TPD and DRIFT spectroscopy it was determined that the Au deposition procedure leads to a significant decrease in OH-group density (mol m−2 BET) on Hombikat, suggesting that the amount of surface OH-groups, rather than the presence or absence of Au, is determining the catalytic performance. The importance of surface OH-groups was demonstrated by comparing the performance of Hombikat (with and without Au deposition) to surface propoxylated TiO2, synthesized by a sol–gel method from titanium (IV) isopropoxide. The effect of the deposition recipe of noble metals on the surface composition of TiO2 should thus be taken into account in evaluating and explaining photocatalytic performance of TiO2 modified by noble metals (Au), in particular in non-aqueous phase reactions. [ABSTRACT FROM AUTHOR]

Structural, textural and surface properties of sulfated and non-sulfated titanium-pillared clay were correlated with catalytic tests in the reduction of NO by NH3 in the presence of oxygen. Lower specific surface areas and basal spacings but stronger acid sites were observed on sulfated Ti-pillared clay than on Ti-pillared clay. Sulfated Ti-pillared clays were more active than Ti-pillared clay. Accordingly, it is suggested that the strong Brønsted acidity generated by sulfate is responsible for the high reactivity of sulfated Ti-pillared clay at high temperature. [ABSTRACT FROM AUTHOR]

Fe-ZSM-5 catalysts were prepared by subliming FeCl3 into H-ZSM-5. The method used allowed Fe-ZSM-5 catalyst preparation by FeCl3 exchange at a desired sublimation temperature and was found to be more precise. The sublimation of FeCl3 into H-ZSM-5 was carried out at 320 and 700 °C. Fe-ZSM-5 prepared by sublimation of FeCl3 at 320 °C followed by rapid heating to 700 °C and the catalyst prepared by subliming FeCl3 at 700 °C were found to be more active for NO reduction with NH3 in the presence of simulated exhaust gases containing water vapor than catalysts prepared by subliming FeCl3 at 320 °C. To determine the active sites, the catalysts were characterized by H2-TPR, in situ DRIFTS of NO adsorption, NH3-TPD, XRD and chemical analysis methods. The observed NO conversion differences in selective catalytic reduction using NH3 could be correlated to the iron cation species present at different locations determined from diffuse reflectance infrared spectroscopy. Enhanced NO reduction activity was obtained when γ positions in Fe-ZSM-5, corresponding to Fe2+(NO) band at 1877 cm-1 in DRIFTS, were preferentially occupied. [ABSTRACT FROM AUTHOR]

A series of Cu catalysts were studied as a function of support (Al2O3, TiO2 and SiO2) and Cu precursor (ex-SO4 and ex-NO3) for activity in the SCR-NH3 reaction. The catalysts were characterized using NOx TPD and SEM/EDAX analysis and the effects of residual sulphur interpreted in terms of site-blocking and NH3 activation mechanisms. [ABSTRACT FROM AUTHOR]

The hydrothermal stability of Ce3+ zeolite catalysts used for selective catalytic reduction of NO x was investigated. Aging of Ce ZSM 5, Ce beta, Ce mordenite and Ce Y catalysts consisted of steaming in 10 or 12 vol% water at 600°C for 3–99 h. Ce ZSM 5 (Si/Al ratios: Si/Al = 17.1, 22.6 and 146.6) and Ce mordenite (Si/Al = 6.4, IE = 77.2%) showed fast deactivation. Ce beta (Si/Al = 12, IE = 68.4%) and Ce Y (Si/Al = 2.8, IE = 122%) are significantly more stable zeolite catalysts, Ce beta being the most active of these two. Ce beta and Ce ZSM 5 catalysts – both having high initial activities – were characterized with 29Si NMR and 27Al NMR. Especially Ce ZSM 5 showed an increase of non framework Al, meaning that the zeolite suffered from dealumination. [ABSTRACT FROM AUTHOR]

Hydrogenation of nitrate in water over Pt-promoted nickel catalysts has been studied with a liquid–gas flow reaction system. While nickel powder obtained from Ni–Al alloy showed an activity for hydrogenation of nitrate (200 ppm) at the initial stage at 333 K, it deactivated rapidly during the reaction. Contrary to this, 1 wt% Pt-promoted nickel exhibited an extremely high activity to NH3 and stability. The reaction rate on 1 wt% Pt-Ni was nearly proportional to the concentration of nitrate up to 5000 ppm, showing that this catalyst is applicable to the treatment of wastewater containing concentrated nitrate. ICP analysis showed that both the platinum and nickel were not dissolved during the reaction. XPS measurement revealed that platinum played an important role in suppression of the oxidation of the nickel surface to retain the active Ni0 surface. [ABSTRACT FROM AUTHOR]